Children and adults with pervasive developmental disorder (PDD), including autism, have been studied with brainstem auditory evoked potentials. Results indicate prolonged neural transmission times are not characteristic of PDD. Other abnormalities seen may be attributable to peripheral audiological factors rather than to brainstem pathology. Adults with childhood diagnoses of autism are in addition, being studied with CT scans, PET scans, neuropsychological testing, psychiatric interviews, and supplementary measures. Results on eight autistic adults and 12 controls suggest normal brain anatomy, diffusely elevated rates of cerebral glucose utilization, and no regions of deficient glucose use. Clinical outcomes include an absence of positive schizophrenic symptoms, a high incidence of concrete and obsessional thinking, compulsive, stereotyped routines, motor stereotypies, deficits in abstract problem-solving, as measured by "frontal lobe" testing, and impairments in social-adaptive functioning exceeding IQ-based expectations. Matched normal and schizophrenic controls are being tested with neuropsychological measures. New projects include cortical evoked potentials, spectral analysis and topographic mapping of EEG, and cerebral blood flow studies of language-disordered dyslexic, visuospatially-disordered dyscalculic, and attention deficit-disordered children and dyslexic and autistic adults. These studies will combine physiological measurement with neuropsychological activation tasks to identify abnormalities in temporal information-processing and to localize dysfunction.